The FBI has declined to discuss was sparked the gunfire, but one law enforcement official told the Post that in the highly-charged "fog of war," an accidental gunshot may have sparked "contagious fire."

“They probably didn’t know whether he had a gun,” another law enforcement source told the Post. “Hours earlier, he and his brother had killed a police officer, shot another officer and thrown explosives out of their cars as the police were chasing them. They couldn’t assume that he did not have a gun and more explosives.”